KG / mm square and loading

[ldavison10]

Hi,
I have been informed by the bracket supplier of a safe load figure of 72.12 kg/mm sq for 8mm threaded rod.

I only know my pipe weights in kg / metre.

How do i calculate if the 72.12 kg/mm sq is of sufficient strength to hang the pipe. Is it simply 72.12 x the cross section of 8mm?

Thanks
Lee

 

[dik]

72.12 kg/mm is 72,120 kg/m or about 48,400 lb/ft... seems a tad high...

Dik

 

[swearingen]

That's kg/mm^2, which comes to about 103ksi, which is the allowable stress of the rod.

For this case you would multiply the 72.12kg/mm^2 by (8mm)^2 x pi / 4 = 3625kg.

That's what the threaded rod will hold. Now take your pipe length and multiply by its weight in kg/m to get its total weight at that bracket. If it's less than 3625kg, it's OK.



If you "heard" it on the internet, it's guilty until proven innocent. - DCS

 

[rb1957]

that'd be mm2, an 8mm rod is 64mm2, 72.12*64 = 4616kg = 10154lbs (maybe a little high for a 5/16" rod ... it'd be a threaded rod, so use the minimum area (which would be less thean this quick calc) ... thinking about it, what does "safe" mean to you ? sustainable load (= ultimate in my biz), about right; = working (= sustainable/SF), sounds high.

i think the load you have is the maximum sustainable load, so you could always test one to see.

 

[rb1957]

ok, i'm a dumb-ass ... thx for pointing that out swearingen !

 

[engvin]

Is the applied load from the pipe is purely shear I would assume 0.6 x the capacity of the rod (ref BS 5950). Generally the load from the pipe for each bracket should also be factored appropriately taking into account its dead weight and the Imposed or live load of the material in the pipe.

 

[hokie66]

engvin,

I think these are hangers loaded only in tension.